Strange, I wonder why this thread was moved from Luthiers Corner to Setup and Repair. Seems to me a control cavity template would be used more for building an instrument instead of repairing one. Either way its not a big deal.
Do you need a template for a bass with the metal control plate, or for one with the controls mounted to the pick guard?
If its a pick guard mounted, I would just do a bath tub rout. If its for a metal control plate, I would trace the plate and mark the screw holes on a piece of paper, and draw a cavity inside the cover as large as you can make it while staying inside your tracing. Then glue the paper to a piece of MDF with spray adhesive and cut it out on on a band saw, or better yet, a scroll saw.
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